A brief 2004 article from Scientific American picking up on McCullough's example of how the urge for revenge parallels the brain activity of a thirsty person about to get a drink of water — but, for money.
In Character, a journal of "everyday virtues" published its "Forgiveness Issue" in September of 2008. It features interviews with a variety of thinkers on the subject of forgiveness, including this interview with Michael McCullough.
Based in the UK, this non-profit organization explores forgiveness, reconciliation, and conflict resolution through real-life human experience. They have an exhibition of stories of forgiveness from ordinary people, including Bud Welch's story of forgiving Timothy McVeigh.
McCullough is a professor of psychology at the University of Miami in Florida, where he directs the Laboratory for Social and Clinical Psychology. He's the author of Beyond Revenge: The Evolution of the Forgiveness Instinct.